Exercise devices, and in particular weight training machines, typically include one or more mechanical members that the user repeatedly moves along a prescribed path for exercise. Conventionally, movement of the mechanical member is resisted in some fashion (often by weights) to render the movement more difficult and thereby intensify the exercise. The movement of the mechanical member determines what muscle or muscle groups are to be involved in the exercise.
One popular exercise movement for weight training is the so-called “pec fly” motion, in which an exerciser moves his arms from an extended position, in which the arms extend sideways from the shoulder, to a flexed position, in which the arms are moved in front of the chest. This exercise movement tends to work, inter alia, the pectoralis major, anterior deltoid, and serratus anterior muscles of the upper body.
Some pec fly machines include a frame, a seat that is mounted to the frame, and a pair of movement arms that are pivotally mounted to the frame. The user sits on the seat, extends his upper arms sideways from his shoulders, engages the movement arms with his elbows, forearms, or hands, and moves his upper arms (and, in turn, the movement arms) to the flexed position in front of his chest. This movement is resisted by weights or other resistance system.
In a typical pec fly machine, the user is seated and the movement arms pivot such that the plane of motion of the user's arms generally parallel to the plane defined by the user's shoulders. This movement is carried out by flexure of the pectoralis major, a fan-shaped muscle, the wider end of which is attached to the sternum. The portion of the pectoralis major that experiences the brunt of the exercise is that portion that is generally parallel with the plane of motion. As a result, the plane of motion of the typical pec fly machine described above described above can provide exercise for the upper portion of the pectoralis major, but typically does not not provide intense exercise for the lower portion of the pectoralis major (which is typically the thicker and more massive portion of the muscle).